drm/i915/fbc: Align FBC segments to 512B on glk+

Apply the same 512 byte FBC segment alignment to glk+ as we use
on skl+. The only real difference is that we now have a dedicated
register for the FBC override stride. Not 100% sure which
platforms really need the 512B alignment, but it's easiest
to just do it on everything.

Also the hardware no longer seems to misclaculate the CFB stride
for linear, so we can omit the use of the override stride for
linear unless the stride is misaligned.

Reviewed-by: Juha-Pekka Heikkila <juhapekka.heikkila@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210921152517.803-3-ville.syrjala@linux.intel.com